\chapter{Acknowledgements}
I would like to thank all the people who have helped and inspired me during the writing of this thesis.

I especially want to thank my tutor Michele Aiello for his guidance during my research. With his enthusiasm and great efforts, he was always accessible and willing to help. I am also grateful to all the people working at ERIS4, who have given me hospitality during this thesis. In alphabetical order they are, apart from my tutor, Stefano Antonelli, Augusto Coppola, Patrizio Munzi, Mario Zullo. In the last 8 months I worked in a company's climate which was cordial and quite where everyone helps each other.

I want to express my gratitude also to Prof. Paolo Merialdo, who during the last years has given me many advices.

I wish to thank all the friends who in the last five years made the university a convivial place to work. They are too many to list them all, but a particular thanks to Giordano Da Lozzo, who is my friend since the high school.

A special thanks is for Chiara Gaetani, who during the last two years has given me the gift of serenity.

Lastly, and most importantly, I wish to thank my parents, Lucia Taccetti and Antonio Barbagallo. To them I will not spend any word, I can only dedicate this thesis.

